Enzed Transport is a blog about rail and general transport in New Zealand. There are two types of postings currently made: transport news headlines from other media, and research articles from the blog author.

Sunday, 10 May 2009

The original railway line south of Dunedin to the satellite township of Mosgiel, a 15 km length, was a steeply graded and sharply curved single-track route incorporating the Caversham and Chain Hills tunnels. It was opened for traffic between 1874 and 1875. It sufficed only for some thirty years before an improvement project was started to make the route fit for heavier traffic and safer, faster operation. Begun in 1906, the modernisation of the line, realigned and regraded into its present day route, was not completed until 1914. A description of the route changes is in order and described thus:

The reconstruction of the route begins with the 1 in 100 grade embankment approximately opposite the CT (Container Terminal) site. This takes the route over Andersons Bay Road on an overbridge and eliminated the first of sixteen level crossings. Just short of the next bridge at King Edward Street, Kensington Station was raised to the new level, which along with the bridge made the working of this station much more straightforward, without the problems of trains blocking the busy road. Continuing south, the next new bridge was built over Wilkie Road. Between it and King Edward Street a siding into the Hillside Workshops makes a steep descent down the embankment. Soon after Wilkie Road as the line passes behind Carisbrook Stadium, the original route level is joined somewhere near the bridge over South Road. Further on the first major deviation was made when a new tunnel was built through the Caversham Hills at a lower level, easing the gradients, and a longer length; it was also double-tracked from the outset. This deviation placed Caversham Station in a new location. On leaving the new tunnel at the south end, Burnside Station was reached on a new site, followed by Green Island. Abbotsford was then encountered, also on a new site, before the second major deviation was reached. This involved a new Chain Hills double tracked tunnel, twice the length of the original and on much more favourable grades. On reaching the south end of this tunnel, Wingatui Station is encountered on a new site nearly 2 km closer to Dunedin than originally. The rest of the route to Mosgiel involved relatively minor changes.

The Caversham Deviation was examined in my previous posting, “Caversham’s Railways” and is not further referenced here. The geographic impact of this deviation was probably the most significant change of the whole project, due to it passing through an established residential area, and its approximate length. Though the Chain Hills deviation was also of significant length, much of the area through which both lines passed, and still pass, is rural and not impacted significantly. The rest of the rebuilding took place on more or less the original route. There was an undeniable geographic impact from the construction of the large embankment between Dunedin and Caversham stations, the three overbridges and raising of Kensington Station, as well as the doubling of the entire line. In the early 1980s, much of the line was singled in several stages; Dunedin-Caversham was completed first, and Caversham-Wingatui later. At this present time, there is still a double track line from Dunedin almost to Kensington including Andersons Bay Road bridge. All of the remaining bridges that were able to be observed have been reconstructed or modified to single track formation. This includes, as at Wilkie Road, removal of the girders on one side, or as in the case of a bridge near the southern end of the Wingatui Tunnel (possibly Abbots Creek), abandonment in place. In other cases like King Edward Street and South Road, the bridges have been rebuilt as a single track structure. The single track in the two tunnels has been pulled towards the centreline to increase the clearances for modern rolling stock.

At the time that the line was altered, it crossed the Dunedin, Peninsular and Ocean Beach Railway line just north of Andersons Bay Road on a diamond crossing. As rebuilt the crossing is effected by a single span overbridge. With the closure of the DPOBR in 1942 the remnant of this line served nearby private sidings. In the late 1980s there were still tracks as far as Orari Street used to store old locomotives. The overbridge still exists even though the track is now cut back to Strathallan Street and appears disused. Green Island and Abbotsford Stations were both junctions of branch lines (Walton Park and Fernhill respectively) in the 1900s. Both of these lines continued in use regardless of the effects of reconstruction which altered the junctions somewhat. Suburban passenger traffic density was an important justification for the reconstructive work at the time; the singling has followed the demise of these trains in 1982, but some of the stations closed earlier, including Caversham in 1962 although it may have continued as a passenger halt after this date. After 1982 the Southerner was the main regular passenger train to pass over the route but it made no stops between Dunedin and Milton. Passenger trains were operated on the Otago Central Railway until 1976 and I do not know if they made any suburban stops within Dunedin city. The advent of the Taieri Gorge Railway has not resulted in any reinstatement of closed stations for passenger convenience, the trains generally running non stop between Dunedin and Wingatui.

During the course of my time in Dunedin I only examined the line between Dunedin and Burnside, although I rode the route twice and obtained a few photos of Wingatui which are in my Otago Central Railway album. Please refer to the Caversham’s Railways article for the map of the route and changes. I am not going to revise that map for the purposes of this article; but the photos from the Picasa web albums associated with this blog will be shown below with brief captions. You can see the full size photos together with locational information if you visit the General album at nztransportgeography's Picasa site.

Heading south from Dunedin, the first indication that most people would see of the reconstruction is the embankment that climbs at 1 in 100 to get the line over Andersons Bay Road, a thoroughfare that it formerly crossed on the level.Here we can see it near the beginning of the ascent.

The bridge over the former DPOBR just north of Andersons Bay Road. The lower line appears to be disused today and any future reconstructive requirement of the bridge would probably result in its disappearance.

Andersons Bay Road bridge. The piers are most probably original. Soon after its construction, movement was reported in one of the abutments; the extent of any remedial work is unknown.

Kensington station was about here when its site was raised on the new embankment about 1906. The date it was closed is not known to me. There is road access today from what is now the Warehouse site, which was formerly the location of the Caledonian Grounds.

King Edward Road bridge. The original design, on the far side, incorporated access to Kensington station by steps between the tracks. These have been removed with the reconstruction of the abutments and piers for the now-singled bridge. I assume the reconstruction was at least partly necessary in order to widen this road. The bridge must therefore have been extended.

This photo by Ken Devlin of Dunedin shows the double track bridge at King Edward Street being singled sometime in the 1980s. Two of the Craven steam cranes were brought out to do this work. In the centre of the far abutment you can see the access doorway to the stairs which went up between the tracks and gave access to the station which was used for suburban passenger traffic. As we can see the abutments were rebuilt later and there was then no need for this access.

Wilkie Road bridge. The abutments are probably original but one of the two girders has been removed as it is no longer needed for a single track crossing.

This substantial retaining wall was needed for the raised embankment where it passed alongside Wilkie Road. At the far end the overbridge can just be seen; the road doglegs under the bridge then continuing in roughly the same overall direction on the other side of the line. The wall was necessary because there was not enough space between the railway and the road to allow for the usual sloping embankment with a wider foot.

The motorway and rail overbridges at South Road, just north of Caversham. The rail bridge is modern, and having a similar substructure as the highway bridge suggests it was probably built at the same time. As the highway was constructed in the 1980s, it would appear to me that the singling of the rail route had been decided by this time, as the rail bridge must have been built from the outset for the single track. (As detailed in the second “Caversham’s Railways” article, the railway used to be where the highway is now, and was deviated to its present location when the highway was put through. This required a new bridge which was built at the same time as the motorway bridge and therefore used a very similar design)